During development of automobiles, the seat pan frame of a vehicle seat is one of the most important safety parts. Generally, the seat pan frames of commonly used seats at present are formed by welding, integral punching or pressing and casting sheet metals. The seat pan formed by sheet metals exhibit greater strength, but it is very heavy and therefore usable area of the sheet metals will be limited due to the weight limitation, which means that the dimension of the seat pan is limited as well.
A flexible and light seat pan has been invented to improve comfort, for instance, the seat pan structures disclosed in Chinese utility models CN203410340U and CN202368420U. Referring to FIG. 8, the flexible seat pan includes a front support sheet metal 100, a rear reinforcing tube 110 parallel with the front support sheet metal, and a number of serpentine springs 120 connected therebetween. The front support sheet metal forms a semi-pan of the seat and the serpentine springs are located at the rear half part of the seat pan to provide flexibility to improve seat comfort. However, this seat pan structure suffers from the following drawbacks: additional fastening means for connecting the springs and the front support sheet metal are needed, and the assembling process is very complex; the springs may be deprived of elasticity or susceptible to breakage because the seat pan structure is not capable of resisting continuous impacts caused by tough roads after having been used for a very short period of time, thereby seating comfort being deteriorated and service life being shortened.
Therefore, a seat pan structure needs to be developed which is light and capable of providing sufficient strength for supporting weight of the seat-taker, is simple in manufacture processing, saves assembly time and exhibits perfect seating comfort.